Isn’t it weird to think that when the slap bet was first conceived back in season two’s “Slap Bet,” it was probably only the second-best invention of the episode (the first being Robin Sparkles)? The series was unstoppable back then. Every plot, big or small, was that strong. It was funny when the bet went awry and unearned slaps were exchanged, and it continued to be funny throughout the course of several seasons, with Marshall owing Barney five slaps to be doled out at his whim.

There was “Stuff,” wherein Barney gets slapped after his excruciating one-man show, and the inaugural “Slapsgiving,” which gave us Marshall’s amazing piano ballad to mark the occasion. Less hilarious was “Slapsgiving 2: Revenge of the Slap,” the episode in which Marshall bequeathed a slap to the others only to end up once again doing the slapping himself, but maybe that was just because of Chris Elliott. In any case, season seven’s superb “Disaster Averted,” when Barney traded in the ducky tie for three additional slaps, got the gag back on track — and that’s the last we heard of this great running joke until now.

The show couldn’t, and still can’t, end before every slap is delivered, and the slowed-down clip at which this happens (about every two years now) has been due mostly to the unknown fate of the series. To be fair, creators Bays and Thomas promised they had a grand plan for the characters, but not necessarily every mythology they created along the way, and fitting two more slaps into the wedding weekend probably posed something of a challenge. I would have much preferred this be a B-plot, with Marshall surprising Barney (and the rest of us) with a slap that complimented another story line, instead of a story line about the slap itself. Never does the series feel more out of gas than when the writers try to wring every last drop from ideas past. But at this point, I get the feeling that they want to serenade their best work, and who can blame them?

So we get a backstory in which Marshall patiently accumulates the skills to deliver the slap of a thousand — nay, a million — exploding suns. The gimmick worked only because the rest of the gang, save Barney, were in on it. But just because the Tarantino-esque chapter titles provide another layer of comedy, is it really that much funnier? Sometimes a reference (to martial arts movies, Kill Bill) is just a reference. Sometimes a nineties R&B act is best left to their rightful decade. (I was more excited by “O Fortuna,” the de facto momentum-building composition, than the totally random Boyz II Men cameo, even if they were singing the aforementioned “You Just Got Slapped.”)

If this episode truly worked, the writers wouldn’t have had to rely on quite so many puns. Don’t get me wrong, every slap-bet episode needs a pun or two, but nothing here (slaptive, slappetite for destruction) rivaled “premature slapulation,” and the repetition came across as filler. Then again, this is not the sort of episode that I think HIMYM does best. My favorites tend to be the ones that mix humor with a little bit of pathos, which is something that no sitcom can manage perfectly every week. If the show is going to suspend reality or rely on references, I prefer something like Community’s stellar spoof of Law & Order; by comparison, “Slapsgiving 3” didn’t try that hard to integrate its source material.

But the pageantry was cute. The titles — particularly “The Some-Might-Call-It-Nitpicky-But-It’s-Really-Just-Thorough Schooling of the Calligrapher” — were a nice touch, and a solid framework. I found myself anticipating each slap master and the winking nod to their real character, with White Flower being DTF and no Mrs. Calligrapher to speak of. The success of the episode was really its acknowledgement of its own limitations. The noodle shop became the de facto meeting place, whether in Shanghai or Cleveland (a.k.a. “the city equivalent of being slapped in the face”), and the best moments were the gang’s uneasy line readings. When Marshall shattered the jukebox, I think I heard Robin say, “The slap of a million exploding stars,” while Ted referred to “exploding tons,” and this was after Marshall himself botched the figure. Naturally, Ted’s contribution to the prank involved backpacking through the fabled forest in college.

Like Marshall says to the kung fu instructor, I have respect, devotion, blah, blah, blah, for this series, but I just want to get to the good stuff already. This diversion was okay, but it wasn’t what I was looking forward to after the last two really strong episodes.

What I liked:

Barney’s assumptions about the measures every man takes to keep his sex life interesting, including numbing one’s hand for “an away-gamer.”

Marshall slapping Ted’s heart out, and the awkward banter of their continued conversation, sort of like when you say your good-byes to a person heading in the same direction. Ted’s slap master was really the best, for being the worst and most boring: “Grammar is the first step on the thousand-mile journey to accuracy.”

The treeway joke. Didn’t really make sense, beyond being yet another pun, but also, the Slapping Tree stood out for logistical reasons. In the original “Slap Bet,” Barney practices his slaps on a tree trunk, so this part of the training doesn’t sound particularly advanced.

Boyz II Men. This didn’t make sense. Backup nostalgia, maybe?

Here’s to the remaining slap. May it come out of nowhere, or never come at all.